1. Field of the Invention
The invention concerns an apparatus for lighting or illuminating spaces, bodies or surfaces, in particular such as a reading light for aircraft, including at least one light source in the form of a white light emitting diode or a luminescence conversion diode, which is connected to a power supply unit.
2. Discussion of the Prior Art
The applicants"" earlier German patent application DE 198 43 330.1 which has hitherto not been published describes an aeroplane cabin lighting arrangement which comprises a plurality of spot-like light sources. Those spot light sources have at least one light emitting diode and are connected to at least one power supply unit. The arrangement of a plurality of spot light sources at or in the ceiling of the cabin of an aircraft provides for uniform illumination of the cabin. The use of light emitting diodes in the spot light sources makes it unnecessary to involve expensive electrical actuation of the cabin lighting. Furthermore the current consumption is considerably lower in comparison with the use of conventional incandescent lamps. Finally, as is known, the service life of light emitting diodes is many time greater than the service life of fluorescent tubes or incandescent lamps so that there is no longer any need for the expensive operation of replacing defective lamps. That prior patent application also already described the point that, depending on the respective density of the spot light sources arranged at the ceiling of the aeroplane cabin, the lighting arrangement can be used as reading lamps over individual seat places. Preferably, the light emitting diodes used are white light emitting diodes which can involve units formed from two-coloured or multi-coloured light emitting diodes or so-called luminescence conversion diodes.
The use of light emitting diodes is also involved in many situations in transport engineering. Thus for example DE 195 14 424 A1 discloses using compatible lenses in relation to two different light sources, for the light of a motor vehicle. This involves a motor vehicle delimitation or position light with a lens which was designed both for illumination with light emitting diodes and also with incandescent lamps. The lens was therefore designed in such a way that it has a set of steps for each of the different light sources, in order to provide for a desired scatter effect in respect of the light source. Overall it is to be stressed in relation to this publication that it only illustrates a delimitation or boundary light, that is to say the amount of light given off is only so much as to detect a contour or delimitation of a vehicle by the rear lights. Lighting or illumination of a surface or a body is not something that this disclosed light seeks to achieve, for which reason that light can be associated with the field of passive lights.
WO 97/26483 discloses a light emitting diode lamp arrangement for use in signal lamps or traffic lights. This publication is also in principles concerned with providing sufficient light in various colours for it to be clearly recognised. For that purpose, the arrangement has a plurality of rows of light emitting diodes which are covered by a stepped lens in correlation therewith. Due to the step configurations of the lens, the arrangement enables the light to be emitted at given angles relative to the beam axis in order to be clearly visible from various angles and under all weather influences.
EP 0 523 927 B1 describes a fluorescent lamp with lens. In that respect, it is to be inferred as essential from that publication that a lens element for a light emitting diode has at least two facets, that is to say lens bodies. The facets, by virtue of refraction, form a desired exit beam.
Proceeding from the above-indicated state of the art as the basic starting point, the object of the invention is to provide an apparatus for lighting or illuminating spaces or rooms, bodies or surfaces, through which at an adjustable spacing from the light source there is attained a brightly lit surface which is relatively sharply distinguished from the surroundings, and which is referred to as an active light.
This structure in accordance with the invention provides a reading light based on light emitting diodes (LEDs) for particular use in air travel. A reading light of this kind is distinguished by a high level of safeguard against failure. The arrangement provides for a maximum amount of light from the light emitting diodes forwardly to the surface to be illuminated. Because of the high degree of reliability of the light emitting diodes, the change which is frequent when using conventional lighting means is no longer required. Furthermore the solution according to the invention affords for reading lights abroad design range and variable structural configurations. Further advantages are as follows:
relatively sharp-edged projection of the light circle is achieved;
the light output is proportional to the quantity of the light emitting diodes;
in tests with subsequent measurements it was found that a quantity of 60 light emitting diodes for a reading light gives optimum results but it is also possible successfully to use smaller and larger quantities; and
narrow lights are possible. which nonetheless produce a sufficiently large light spot.